This invention relates to conveyor belts and, more particularly, to modular plastic conveyor belts formed of rows of plastic belt modules pivotally interlinked by transverse pivot rods.
Because they do not corrode, are light weight, and are easy to clean, unlike metal conveyor belts, plastic conveyor belts are used widely, especially in conveying food products. Modular plastic conveyor belts are made up of molded plastic modular links, or belt modules, that can be arranged side by side in rows of selectable width. A series of spaced apart link ends extending from each side of the modules include aligned apertures to accommodate a pivot rod. The link ends along one end of a row of modules are interconnected with the link ends of an adjacent row. A pivot rod journaled in the aligned apertures of the side-by-side and end-to-end connected modules forms a hinge between adjacent rows. Rows of belt modules are connected together to form an endless conveyor belt capable of articulating about a drive sprocket.
In many industrial applications, conveyor belts are used to carry products along paths including curved segments. Belts capable of flexing sidewise to follow curved paths are referred to as side-flexing, turn, or radius belts. As a radius belt negotiates a turn, the belt must be able to fan out because the edge of the belt at the outside of the turn follows a longer path than the edge at the inside of the turn. In order to fan out, a modular plastic radius belt typically has provisions that allow it to collapse at the inside of a turn or to spread out at the outside of the turn.
Apertures slotted in the direction of travel of the belt are commonly provided in the link ends on at least one side of the modules to facilitate the collapsing and spreading of the belt.
In applications where greater strength is required radius belts with a larger pitch are required. These radius belts with a large pitch (xe2x89xa71.5xe2x80x3) have suffered from the disadvantage that, due to the larger pitch and the need to be collapsible, the grid openings were large enough to allow the finger of operators to penetrate the grid. This situation may lead to injuries.
What is needed is a modular radius conveyor belt that has a large pitch yet reduces the gap between the links to less than 10 mm to prevent fingers from penetrating the grid.
The present invention meets the above-described need by providing a radius belt having belt modules with a cross-rib designed so as to allow the link ends to undercut the cross-rib when collapsing. The module has a cross-rib with an extended portion in the longitudinal direction. The modules include first and second module surfaces, i.e., a top, product-conveying surface and a bottom, sprocket-driven surface. A cross-rib extends across the width of each module transverse to the direction of belt travel. The cross-rib is formed in part by a web and in part by a thin, corrugated strip having a pair of essentially parallel walls. The corrugated strip forms a series of regularly spaced alternating ridges and valleys along each wall. Link ends extend outward from the ridges on each wall of the corrugated strip. Each link end has a leg portion attached at a ridge of the strip and a thick distal portion at the end of the link end distant from the corrugated strip. Transverse holes in the link ends extending from respective walls of a module are aligned to accommodate a pivot rod. When the link ends of consecutive rows of side-by-side modules are intercalated, the pivot rod serves as a hinge pin in a hinged joint between consecutive interlinked rows. To permit the belt to follow a curved path, the pivot rod openings in at least one of the link ends extending from one of the walls of the corrugated strip are slotted longitudinally in the direction of belt travel.
The belt is driven by engagement of the sprocket tooth with the curved outside surface of the link ends. The link end engaged by the sprocket tooth is subjected to a compressive force rather than an undesirable tensile force. Thus, the link ends provide pull strength, resistance to belt and sprocket wear, and sprocket drivability. As an alternative, a central portion of a link end disposed in the middle belt modules may also engage with a tooth on the drive sprocket. Because the mid modules do not have to collapse fully, they may be formed with a thicker and fully straight cross-rib.
Each wall of the corrugated strip forms a series of arched recesses with the leg portions of the link ends. The recesses are large enough to provide room for a thick link end of an interlinked module of an adjacent row to collapse into the recess or to rotate as belt rows fan out going around a turn. Because the recesses along one wall overlap in a transverse direction with the recesses along the other wall, additional space for collapsing is provided.